<template>
  <div class="spec-preview">
    <img :src="skuImageList[defaultIndex]?.imgUrl" />
    <div class="event" @mousemove="zoomMouseMove"></div>
    <div class="big">
      <img ref="bigImg" :src="skuImageList[defaultIndex]?.imgUrl" />
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
export default {
  name: "Zoom",
  props: ["skuImageList","defaultIndex"],
  methods: {
    zoomMouseMove(e) {
      //获取鼠标到达容器边缘的距离
      const mouseToBox = {
        x: e.offsetX,
        y: e.offsetY,
      };

      //获取蒙版的一半的宽度
      const maskWH = {
        w: this.$refs.mask.offsetWidth / 2,
        h: this.$refs.mask.offsetHeight / 2,
      };

      //计算蒙版需要移动的距离
      const maskLocation = {
        x: mouseToBox.x - maskWH.w,
        y: mouseToBox.y - maskWH.h,
      };

      //临界值判断
      if (maskLocation.x <= 0) {
        maskLocation.x = 0;
      } else if (
        maskLocation.x >=
        e.target.clientWidth - this.$refs.mask.offsetWidth
      ) {
        maskLocation.x = e.target.clientWidth - this.$refs.mask.offsetWidth;
      }
      if (maskLocation.y <= 0) {
        maskLocation.y = 0;
      } else if (
        maskLocation.y >=
        e.target.clientHeight - this.$refs.mask.offsetHeight
      ) {
        maskLocation.y = e.target.clientHeight - this.$refs.mask.offsetHeight;
      }

      //赋值
      this.$refs.mask.style.left = maskLocation.x + "px";
      this.$refs.mask.style.top = maskLocation.y + "px";

      //经计算比例是2，给大图移动赋值
      this.$refs.bigImg.style.left = -maskLocation.x * 2 + "px";
      this.$refs.bigImg.style.top = -maskLocation.y * 2 + "px";
    },
  },
};
</script>

<style lang="less">
.spec-preview {
  position: relative;
  width: 400px;
  height: 400px;
  border: 1px solid #ccc;

  img {
    width: 100%;
    height: 100%;
  }

  .event {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 998;
  }

  .mask {
    width: 50%;
    height: 50%;
    background-color: rgba(0, 255, 0, 0.3);
    position: absolute;
    left: 0;
    top: 0;
    display: none;
  }

  .big {
    width: 100%;
    height: 100%;
    position: absolute;
    top: -1px;
    left: 100%;
    border: 1px solid #aaa;
    overflow: hidden;
    z-index: 998;
    display: none;
    background: white;

    img {
      width: 200%;
      max-width: 200%;
      height: 200%;
      position: absolute;
      left: 0;
      top: 0;
    }
  }

  .event:hover ~ .mask,
  .event:hover ~ .big {
    display: block;
  }
}
</style>
